Specialty Gases for VOC Analyses

It is generally recognized that some volatile organic compounds (VOCs) can have severe, negative influences on human health. Certain VOCs can constrain normal function of the central nervous system, causing headaches, fatigue, drowsiness, and discomfort, and a number of VOCs have even been proven to be carcinogenic. Legislation around VOC emissions is becoming increasingly stringent, with severe financial penalties often the outcome for non-compliance. Detection and analysis of industrial VOCs now demands continuous innovation to assist companies in complying with tightening regulations. This article looks at the role of specialty gases in monitoring, detection, and analysis of such emissions.

(PHOTO CREDIT: JULIA DAVILA-LAMPE/GETTY IMAGES)

The number of processing plants coming on stream worldwide continues to increase, bringing the release of volatile organic compounds (VOCs) into the atmosphere under intense scrutiny by environmental authorities. For example, the United States Environmental Protection Agency (US EPA) regulates the emissions of VOCs to prevent ground-level ozone formation, a key constituent of photochemical smog.

The risks associated with industrial VOCs are aggravated by the fact that hazardous concentrations are usually very low and the health issues they can cause can be accumulative and slow to develop. It has been reported that asthma and other respiratory diseases are on the rise, affecting both young and old, and VOCs have been implicated. VOCs can cause sensory stimulation, tissue inflammation, anaphylaxis, and nerve toxic reactions; some can also impact the normal function of the central nervous system, causing headaches, fatigue, drowsiness, and discomfort. Research indicates that alcohols, aromatic hydrocarbons, and aldehydes have the potential to stimulate mucous membranes and upper respiratory tracts. Furthermore, a number of VOCs are proven carcinogens or potential carcinogens, such as benzene, trichloroethylene, and formaldehyde. More disturbing is that the concentrations of VOCs can be greater inside a building than in the ambient air outside because of emissions from paint on the walls, carpets and furniture. Many researchers around the world have presented papers on Indoor Air Quality or IAQ. The Japanese even have a more descriptive name for this, Sick Building Syndrome.1

By measuring ambient air, processing plants are able to determine if any of their raw materials, process intermediates, or end-products are in the air and, if so, determine the emission source. In the petrochemical industry, this applies to a broad spectrum of components.

Solvents are a major source of man-made VOCs that when exposed to higher temperatures, such as in a production process exhaust stream, evaporate and enter the atmosphere where they create a foul smell. There are several different technologies to reduce or remove solvents from exhaust streams and reuse depending on the recovery value and concentration of the solvents.

One of the most effective ways to recover solvent vapours is to condense and capture them using liquid nitrogen as a cooling media in a process called low temperature or cryogenic condensation. When liquid nitrogen is used to cool the condenser, VOC emissions are rapidly reduced to low levels by trapping the VOCs at extremely low temperatures. They can then be reintroduced to the industrial process.

Increasing regulatory requirements have created more rigorous demands in measurement and, with new compounds to evaluate, laboratories performing environmental analysis of air quality are continually faced with new challenges. The growing demand for accurate identification and quantification of VOCs across both ambient and indoor environments has initiated requests from chemical analysts around the world for low-level multi-component VOC calibration gas mixture standards.

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